The present invention relates generally to blade tracks for gas turbine engines. More specifically, the present invention relates to a blade track support assembly having controlled thermal expansion properties.
A gas turbine engine is typical of the type of machinery which the invention described herein may be advantageously employed. It is well known that a gas turbine engine conventionally comprises a compressor for compressing inlet air to an increased pressure for combustion in a combustion chamber. A mixture of fuel and the increased pressure air is burned in the combustion chamber to generate a high temperature gaseous flow-stream for causing rotation of turbine blades within the engine. In an effort to reduce specific fuel consumption of engines, there has been a move to increase the efficiency of the turbine by decreasing the clearance between the rotating turbine blade tips and the stationary blade track. In designing a gas turbine engine with tighter blade tip clearances, designers must account for transient conditions that the gas turbine engine experiences during operation. During acceleration of the gas turbine engine, the rotor carrying the turbine blades experiences mechanical growth in a radial direction faster than blade track/shroud, thereby allowing the potential for mechanical contact between the blade tips and the blade track/shroud. During deceleration of the gas turbine engine, the blade track/shroud exhibits mechanical shrinkage in the radial direction more quickly than the rotor, thereby allowing the potential for mechanical contact between the blade tips and the blade track/shroud.
The present invention seeks to control the clearance between the blade tips and the blade track/shroud by lowering the thermal expansion of the blade track support assembly, thereby allowing a reduction in the steady state run clearance between the blade tip and the blade track/shroud. The resulting improvement is manifested as an increase in turbine efficiency and a reduction in specific fuel consumption. The present invention provides a novel and non-obvious blade track/shroud assembly for a gas turbine engine.